Tree of the Week: Devilwood (Osmanthus americanus)

Back in December we added a young devilwood to the arboretum catalogue. There are now two devilwoods growing in the arboretum, in very different locations. You can read about the senior devilwood here. The new addition can be found in a sunny spot near the Fitness Center. It was grown by Dr. Gladden Willis on his tree farm in Webster Parish.

Devilwood (Osmanthus americanus) is known for its evergreen leaves and persistent, dark blue drupes that ripen in the fall.

There are quite a few fruits on our little tree—pick a few, take them home, and try your luck at germinating them.

Drupes are approximately ⅜ inches in diameter. According to the University of Florida IFAS Extension, you are in for a challenge if you try to germinate these drupes: "Propagation is by cuttings or seed, and is difficult by either." Please don't attempt any cuttings with our little tree!

Tree of the Week: Green Ash (Fraxinus pennsylvanica)

Our tree of the week is the arboretum's lone green ash (Fraxinus pennsylvanica). It's the big tree, all by itself, pictured center. In 1998, this specimen was collected from the Walter B. Jacobs Memorial Nature Park in Caddo Parish. It was planted the same year.

Our green ash is located outside of the arboretum proper, between the Student Union Building and the Hargrove Memorial Amphitheater.

This ash tree grows on a grassy slope without competition for sunlight. Its solitary existence has allowed it to develop vertically and laterally unhindered, giving us an opportunity to appreciate its form. What we have today is a thoroughly upright individual, with a single straight trunk and an oval head.

Looking at the trunk, we see that its lower branches have been removed, but the remaining branches droop enough to allow for up-close leaf-inspection. A bed of pine straw around the base of the trunk reduces weeds growing among the numerous surface roots.

Surface roots growing in an otherwise flawless lawn are a headache for those tasked with mowing the grass.

The bark is gray, rough, and furrowed. The narrow ridges interlace in some places, creating a diamond pattern.

This species is known as a dependable shade tree.

All of that much desired shade is made possible by these large, dark-green, glossy, pinnately-compound leaves. The leaf pictured above has seven leaflets and measures 10 inches in length. Leaflet shape varies. On this leaf, we see ovate and lanceolate shaped leaflets, with acuminate tips and wavy margins.

Leaflet length varies, too.

Underneath, leaves are pale-green and smooth.

Overall leaf-length and number of leaflets varies as well. Here we have a leaf that measures a foot in length with only five leaflets.

You can find more images of this individual here. Be sure to compare the older photo of the bark with the current photo.

For more information about this species please consult the following online sources:
United States Department of Agriculture
Louisiana Plant Identification and Interactive Virtual Tours (LSU AgCenter)
University of Florida IFAS Extension

Tree of the Week: Fringe Tree (Chionanthus virginicus)

Fringe trees (Chionanthus virginicus) are flowering in northwest Louisiana. You can find them on the Centenary campus, around town, and growing wild in Caddo parish. This tree takes on different shapes depending on the growing conditions. In the arboretum, you can study fringe trees grown in low-light, part shade and full sun conditions. Trees grown in full sun, like the individual pictured below, tend toward a multi-trunk habit.

Our tree of the week is a diminutive, shrubby fringe tree, covered in the eponymous fringe flowers. This individual is 6-years-old. It's an arboretum volunteer, first identified as a tiny seedling, growing under a hawthorn -- not the best location for its development.

During the winter of 2013, soon after it was identified, the little seedling was transplanted to this very sunny location, on a steep slope south of Mickle Hall, and near the Ratcliff Gazebo.

For such a young tree, its flower production is marvelous. These flowers have a faint, sweet fragrance.

This fringe tree has taken on a multi-stemmed form, resembling a shrub.

A panicle was snipped for closer inspection.

The panicles are long, and clustered with white flowers.

Each flower is slight, very delicate.

Petals are very thin, but long, measuring approximately an inch in length.

Tree of the Week: Pumpkin Ash (Fraxinus profunda)

The arboretum's pumpkin ash (Fraxinus profunda) is pictured center, growing next to the white bridge. In October 1990, it was purchased from Woodlanders Nursery (Aiken, SC), and it was planted shortly after its arrival. This pumpkin ash has an upright habit with drooping branches. The lower limbs have been removed. Over the past several decades, it has grown in competition for sunlight, resulting in a noticeable bend in its trunk.

Authorities often classify this species as a swamp tree. It's commonly found growing with bald cypresses and water tupelos. Professor Leuck wisely selected a wet location for this pumpkin ash. It grows on the east side of the arboretum stream.

An old wax myrtle (Myrica cerifera) is pictured behind the pumpkin ash, on the opposite side of the bridge. Two large water oaks (Quercus nigra) are pictured to the right, further up the slope. The pumpkin ash competes with these old oaks for sunlight.

Under the bridge, the roots of the pumpkin ash blend in with the landscape rocks.

The pumpkin ash roots have spanned the stream, serving as a natural weir, slowing down the flow of water. Frogs and other 'little fellers' will have to clamber over the obstacle.

The pumpkin ash is known for having a swollen trunk. The base widens over time. Our 30-year-old specimen is developing this characteristic.

The base of the trunk gradually slopes outward.

This is a detail of the bark from the base of trunk. The dark gray bark is rough and divided into small strips and blocks. The pattern is well worth observing closely. What can you see here?

Further up the trunk, the bark is lighter gray with larger, longer fissures dividing the vertical-looking plates.

A volunteer Virginia creeper (Parthenocissus quinquefolia) has been allowed to climb the trunk. It's very hairy! Check out this publication for a photo showing the difference between a hairy poison ivy and a hairy Virginia creeper.

This Virginia creeper vine has a firm hold on the bark of the pumpkin ash. 

Looking up at the bare branches, we see the silhouetted clusters of flowers and new leaves.

The pumpkin ash branches droop down low to the ground, allowing us the opportunity to study the new growth and to snip a few branchlets for further investigation.

On this twig we see two new leaves, opened staminate flowers and unopened flower buds.

Here we have a couple of new, compound leaves, stuck together.

The flower buds appear in pom-pom clusters.

When vigorously rustled, these staminate flowers release a tiny plume of pollen.

Pumpkin ash flower buds

For more information about this species consult the following:
United States Department of Agriculture -- be sure to zoom-in on the distribution map
U.S. Forest Service
Louisiana Plant Identification and Interactive Virtual Tours (LSU Ag Center)
Virginia Tech Dendrology

Tree of the Week: Fringe Tree (Chionanthus virginicus)

This week in the arboretum you can observe the beautiful, blue fruits of the fringe trees (Chionanthus virginicus). The best viewing location is on the west side of the Fitness Center. There you'll find a grouping of fringe trees with heavily ornamented branches. Fringe tree fruits resemble olives, and they look good enough to eat. Unfortunately, these fruits are inedible. Removal of the outer blue covering reveals a single inedible seed.

In 2002, four Caddo parish seedlings were planted near the Fitness Center along the concrete drainage. Over the years, the four individuals have grown together, forming a bush. The Fitness Center blocks the morning sun, but in the afternoon, this is very sunny spot.

Looking westward, we see the gradual slope leading up to Cline Hall dormitory. A bald cypress (Taxodium distichum) is pictured to the left of the fringe trees, and on the right side of the frame, we see the outstretched limbs of a pond cypress (Taxodium ascendens). All three species appreciate the extra water that runs down the hill.

After more than 15 years in the ground, the fringe trees are still small, with slender trunks. A couple of the individuals could be pruned back to a single-stem form, but overall the individuals have multi-stemmed forms, resembling shrubs rather than trees.

Fringe trees have dark green leaves which will make it difficult to see the fruits from afar. In order to appreciate the subtle beauty of the innumerable fruits,  you will need to get up close and personal with the trees.

The ovoid fruits resemble fresh olives.

Fringe tree fruits hang from long panicles.

Fruits measure approximately half an inch in length.

Some fruits are a little larger, measuring over half an inch.

Each fruit is a drupe. A little liquid is released when squeezing the fruit, and after the blue covering is removed, a single, large seed is revealed.

You can find more photos of the arboretum's fringe trees here.

For more information about this species consult the following:
United States Department of Agriculture
Texas A&M University (Aggie Horticulture)
NC State University
University of Florida (IFAS Extension)